Liquids, as used in some industries, are required to be ultrapure. These ultrapure liquids are free or substantially free from: minerals, ions, and gas. The removal of minerals and ions is most often accomplished through a reverse osmosis process. The reverse osmosis process, however, does not remove the dissolved or entrained gases. The most common dissolved or entrained gas is air, which has as its major components nitrogen, oxygen, and carbon dioxide.
In the past, membrane contactors, for example, hollow fiber membrane contactors have been used to remove or add dissolved or entrained gases from or to a fluid. Hollow fiber membrane contactors are known. For example, see U.S. Pat. Nos. 3,288,877; 3,755,034; 4,220,535; 4,664,681; 4,940,617; 5,186,832; 5,264,171; 5,284,584; 5,352,361; and 5,449,457. Hollow fiber membrane contactors are commercially available under the name of LIQUI-CEL® from Membrana a division of Celgard Inc. of Charlotte, N.C. and under the name of SEPAREL® from Dainippon Ink and Chemicals of Tokyo, Japan. Some contactors are assembled from several pieces that are sealed with a plurality of O-rings, and then, they are mechanically fastened (e.g. clamped) together. Such contactors have numerous uses, one being the degassing of liquids.
To facilitate manufacture of these contactors, the hollow fiber membranes are typically formed into a fabric (e.g., woven or knitted). The fabric is wound around a mandrel (e.g., a perforated center tube) and fixed into place by potting the fabric edges, with either thermosetting or thermoplastic materials, to form a unitized structure. See, for example, U.S. Pat. Nos. 4,940,617 and 5,284,584. This unit can then be inserted within a shell (housing) and sealed, i.e., with or without O-rings, to make a membrane contactor. See, for example, U.S. Pat. No. 6,207,053.
Most hollow fiber membrane contactors with small diameters are made by integrally potting the unit inside the housing. This eliminates the need to provide or maintain any additional seal therebetween the unit and the housing via other means, i.e. O-rings, or gaskets. However, the contactor components (e.g., shell, end cap, center tube, microporous membranes and potting) are made from dissimilar materials that makes the joining a difficult problem. In addition, the demand for these contactors requires that improvements be investigated and utilized.
Accordingly, there is a need for an improved high performance mini hollow fiber membrane contactor.